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A newly discovered greenhouse gas of industrial origin is more powerful than any previously known.

Bubbles of the sulphur-based compound SF5CF3, previously unknown in the atmosphere, were found in snow samples from Antarctica. Comparison with deeper snow layers revealed the compound is now present in the atmosphere at ten times the concentration of 100 years ago.

The discovery of SF5CF3 (trifluoromethyl sulphur pentaflouride) was published in the journal Science in a collaboration between the Max Planck Institute for Chemistry, the University of East Anglia, the Ford Motor Company, the University of Reading, the University of Frankfurt the British Antarctic Survey, and the Natural Environment Research Council in Cambridge.

The researchers found that the increase of SF5CF3 in the atmosphere appears to be coupled with an increase of the very inert gas sulfur hexaflouride (SF6), suggesting a common source.

"There is no doubt that the new gas SF5CF3 is made by industry, or is produced during certain process involving industrial gases, but its exact source remains a mystery," they said.

SF5CF3, which is closely chemically related to SF6, originates as a breakdown product of SF6 in high voltage equipment. SF6 is used in electrical switches to suppress sparks, in protecting metals during a melting process, in tennis balls, car tyres and even previously in running shoes. However because it is a strong greenhouse gas, SF6 production is now restricted under the Kyoto Protocol.

SF5CF3 is an even stronger greenhouse gas, according to the researchers. It has the largest radiative forcing on a per molecule basis of any gas found in the atmosphere (0.57 W/m2 ppb - parts per billion). Radiative forcing is a measure of heat flux, based on how strongly a molecule absorbs infrared radiation.

The icey evidence from Antarctica shows that SF5CF3 levels have shot up ten times in the past century. Researchers found that, in the surface layers of Antarctic snow, atmospheric bubbles of SF5CF3 have been trapped in the ice at a concentration of 0.1 ppt (parts per trillion). But at 100 metres deeper into the snow (dating back to around the year 1900) the concentration is only 0.01 ppt.

While this is still an extremely low concentration, SF5CF3 has one feature which makes it a real cause for concern, according to Dr Paul Fraser from CSIRO Atmospheric Research.

"Although there's not much in the atmosphere at present, the molecules of this gas are so long lived that you can't get rid of them," he said. "There's almost a philosophical problem with producing molecules that nature can't get rid of."

Dr Fraser said the Kyoto Protocol would have to address the issue, given how long lived SF5CF3 would be in the atmosphere.